There are many commercially available organosiloxane coupling agents useful to improve bonding between different materials. For example, coupling agents may be used to promote adhesion between a filler and a resin in the manufacturing of composite films, or they are coated onto film surfaces to promote adhesion to other materials and/or surfaces.
Generally, siloxanes are hydrolyzed in water and can be applied to surfaces of a substrate by any conventional in-line method, such as spray coating or roll coating. Once the siloxane coating has dried, the resulting primed surface is receptive to direct extrusion coating with one or more polymers.
Additionally, siloxanes are particularly useful as coupling agents in the production of thermoplastic composite materials and unsaturated polyester composite materials. Siloxanes can also be used as primers in adhering thermoplastic resins or unsaturated polyester resins to various substrates.
U.S. Pat. No. 4,177,175 discloses a pigment-free aqueous coating dispersion of an organothiolsesquioxane and colloidal silica for used as an adhesion additive for silane resins having a low degree of substitution. The coating solution can be applied to solid substrates such as polymeric sheets by conventional methods of flowing, spraying or dipping, to form a continuous film.